The Hawaiian island of Oahu held a position of the first importance in the
military structure of the United States before and during World War II. During
the prewar years Oahu and the Panama Canal Zone were the two great outposts
of continental defense, and, after Japan plunged the United States into a Pacific
war, Oahu became an essential springboard for the offensive that was finally
to crush the Japanese Empire.

What gave Oahu its military importance was the great naval base of Pearl Harbor.
The Army had primary responsibility for protecting Pearl Harbor and, to fulfill
this responsibility, before the war it maintained on Oahu its largest and, in
many respects, its best equipped overseas garrison. The Army's objective was
to make Oahu impregnable, and in April 1941 the War Department confidently
described the island as the strongest fortress in the world.1 Seven months later
this confidence was rudely shaken by Japan's amazingly successful attack on
a major portion of the Pacific Fleet berthed and moored in Pearl Harbor, and
on the Army's surrounding air installations and aircraft on the ground. The
background of this Japanese venture has been one of the most intensively studied
and related episodes in modern history, and this volume can add only some detail
about what the Army did before and during the attack.2

earlier, immediately after the United States annexed the Hawaiian Islands in
August 1898. Increasing Japanese-American friction in the following decade led
to a decision by the Army and Navy in 1908 to make Pearl Harbor the principal
American naval bastion in the Pacific.3 To protect Pearl Harbor, the Army greatly
expanded its Oahu garrison and in 1913 established the Hawaiian Department as
an independent command under direct War Department control. In the two
decades after World War I the Army kept about it percent of its manpower on
Oahu, built up formidable coastal defenses on its south shore to protect Pearl
and Honolulu harbors, and installed air defenses to guard vital installations
against this new element of warfare that developed so rapidly between world
wars.

The Army's mission in Hawaii was defined in 1920 as the defense of the Pearl
Harbor naval base against "damage from naval or aerial bombardment or by
enemy sympathizers" and against "attack by enemy expeditionary force
or forces, supported or unsupported by an enemy fleet or fleets."
4 The
mission remained essentially unchanged until 1941, and until that year
the Army did almost nothing to guard the other major islands of the Hawaiian
chain against attack. In February 1941, General Marshall broadened the stated
mission informally by emphasizing the responsibility of the Army for protecting
the fleet as well as the Pearl Harbor naval installations.5 In practice, as
events were to prove, the impact of this new instruction was blunted by the
common assumption in Washington and Hawaii that no serious attack on Oahu was
at all likely if the bulk of the fleet was present in Hawaiian waters.

The eight major islands of the Hawaiian chain are situated about 2,400 statute
miles southwest of the California coast, and about 3,900 miles from the principal
Japanese island of Honshu. The main island group extends nearly 400 miles from
Hawaii-the large island which has nearly two-thirds of the total land area-northwestward
to Kauai and Niihau. (Map II) Hawaii, Maui, Oahu, and Kauai
are the principal islands, and the latter three are roughly of the same size.
All are mountainous islands of volcanic origin, possessed of a subtropical climate
that is pleasant and healthful. Oahu, the third largest island with an area
of 604 square miles, owes its preeminence to two harbors along its southern
shore: that of Honolulu, and the shallow lagoon seven miles to the west that
after intensive development became the Navy's largest overseas base. Oahu, with
less than one-tenth of the archipe-

lago's area, had 60 percent of its population in 1940, and nearly 70 percent
by the end of the Pacific war. The population of all the islands is something
of a racial kaleidoscope. The largest single element in 1940 was of Japanese
descent-roughly, 37 percent of the total of 423,000. On both Hawaii and Kauai
those of Japanese descent outnumbered those of Caucasian descent by three to
one, and on Oahu the two groups were about equal in number. Although more than
three-fourths of the people of Japanese descent were American-born citizens,
their preponderance in the total population had a profound influence on military
thinking about what might happen in a war with Japan. Most Army and Navy officers
assumed that in the absence of close military control there would be widespread
attempts at sabotage, and therefore they planned for a wartime establishment
under martial law. The existing Hawaiian government was that of a fully incorporated
territory, with an elected legislature and a nonvoting delegate to Congress,
and executive and judicial officers appointed by the President. It had
jurisdiction over the main archipelago, the chain of minuscule reefs extending
a thousand miles from Kauai to Midway, and two distant coral islands to the
southwest.

Oahu is a diamond-shaped island having two parallel mountain ranges, which have
precipitous slopes to the seaward and a broad plateau in between that spreads
out as a coastal plain in the south. Before World War II Oahu's Army and Navy
installations were mostly on this plateau and plain. There they were so closely
intermingled and integrated with the civilian population and general economic
activity of the island that military secrecy on any large scale was impossible.
The Army had its headquarters at Fort Shafter in the western outskirts of Honolulu,
but the main body of its troops was stationed at Schofield Barracks in the center
of the plateau about ten miles inland from Pearl Harbor. The principal Army
unit was the Hawaiian Division, activated in 1921; and its station at Schofield
covered the Pearl Harbor base against an enemy landing on the northwest coast.
It was only along this coast that the Army believed a hostile landing in force
even remotely feasible. The principal Army air installations were Hickam Field,
the base for bombardment aviation, adjacent to Pearl Harbor on the Honolulu
side, and Wheeler Field, the pursuit and fighter base located in the interior
next to Schofield Barracks.

On the day war began in Europe in September 1939, the Army commander in
Hawaii, Maj. Gen. Charles D. Herron, after "taking stock" of his local
outlook, informally commented to General Marshall that he would not "want
to be given the job of cracking the nut" which Oahu presented to any would-be
invader, because of its "encircling reefs and two coasts pro-

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tected by very difficult small mountain ranges and the south shore very heavily
armed [and therefore with the] prospect of fighting an entrenched division all
the way across after a landing on the north shore." He admitted that Oahu
was difficult to defend against "air attacks coming in from the sea."
But he expressed the belief that airplane carriers could "not live in these
waters as long as we have left any bombers at all;" and anyway he felt
"that naval air forces, like the cavalry of old, always has in its mind,
the get-away."
6 General Herron's optimism about Oahu's relative invulnerability
to invasion appears to have been well founded, but two years later the Japanese
certainly belied his observation about carriers.

The possibility of war with Japan had led the Army and Navy in 1924 to draft
a new joint ORANGE plan to govern the conduct of such a war. Since the Limitations
of Armament Treaty of 1921 barred the building of any new military defenses
to the westward of Hawaii, the Pearl Harbor base and its Army defenses assumed
an ever-increasing importance in Pacific war plans during the twenties and thirties.
By 1938 the Navy had expended about $75,000,000 on this base, and the Army more
than twice that amount on military installations to protect it. Navy plans for
a Japanese war visualized the launching of a transpacific offensive from Oahu
through Japanese-held islands toward the Philippines; but by 1935 the Army was
convinced that such an offensive was impracticable, at least at the beginning
of a war with Japan, and therefore that American strategy in the Pacific should
be essentially defensive and should concentrate on holding the Alaska-Hawaii-Panama
line. The last ORANGE plan revision of 1938 represented an unsatisfactory
compromise of the Army and Navy positions. In any event, because of the
increasing threat of war with Japan, the Army from 1935 until the autumn of 1939
accorded the Hawaiian Department top priority in the supply of equipment, and it
increased the strength of the garrison by more than 50 percent, from 14,821 to
21,289 between the summers of 1935 and 1938.7

In September 1935 General Herron's predecessor in Hawaii, Maj. Gen. Hugh A.
Drum, had expressed himself as far from satisfied with either the peacetime
or planned wartime allotments of men and material to his department, and
he also wanted to broaden the Army's mission. General Drum proposed that
the mission include defense of all the main Hawaiian islands and participation
in the air defense of the eastern Pacific area. He asked for

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twenty-six of the new "flying fortress" heavy bombers then under
development, and he proposed to construct operating fields for them on
Hawaii and Kauai islands. This measure in turn would require some deployment
of Army ground forces to the outer islands to protect the new airfields. The
War Department rejected these proposals on the ground that the defense of ocean
areas was the Navy's business and that the dissipation of Hawaii's forces would
weaken the defense of Pearl Harbor, which must remain the overriding mission
of the Army in Hawaii. Army plans of 1935 called for a war garrison on Oahu
of more than 100,000 officers and men, and the Army planners in Washington rejected
General Drum's proposal that 23,000 of these troops be put on the outer islands
in wartime.8 The
Joint Board confirmed these actions and held that the mission of United States
forces in Hawaii was only "to hold Oahu as a main outlying naval base" and the
Army's specific mission was "to hold Oahu against attacks by sea, land, and air
forces, and against hostile sympathizers."
9

After a lengthy maritime strike in the winter of 1936-37 General Drum resubmitted
his recommendations with the argument that the Army must extend its protection
to the outer islands if it wished to assure an adequate supply of food for Oahu
in time of war. Oahu produced only 15 percent of its own requirements in food,
but the other islands could readily make up the deficiency in an emergency if
communication was maintained with them. Again the War Department objected. In
both 1935 and 1937, its basic argument against broadening the Army mission
in Hawaii was the following: "If the Fleet is in the Pacific and free to
act, Oahu will be, with the completion of the existing defense project,
secure against any attacks that may be launched against it. It is only in the
case that the Fleet is not present or free to act that the security of the Hawaiian
Islands can be seriously threatened."
10 That the presence of the fleet
in or near Hawaiian waters provided a more or less automatic guarantee against
any serious attack on Oahu continued to be a widely held conviction both in
Washington and Hawaii until the Japanese demonstration to the contrary in December
1941.

A fresh survey of Oahu's defenses, conducted in late 1937 by Col. Edward M.
Markham on oral instruction of the President and Secretary of War, produced
conclusions similar to those of General Drum.11 Colonel

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Markham stressed the need for making the Pearl Harbor base as nearly impregnable
as possible. He pointed out that despite their recent strengthening, the Army's
installations for defending it were considerably less than impregnable,
principally because of "the astounding advance in aircraft design and range
over the past twenty years." He emphasized as "a corollary of the
first order" the importance of preventing an enemy from seizing and using
Oahu and its Pearl Harbor base "as a springboard of attack against our
west coast territory and shipping, and the Panama Canal." Colonel Markham
agreed with General Drum that substantial peacetime Regular Army garrisons
should be installed on Hawaii and Kauai to operate and support new air bases
and to assure Oahu of food in an emergency. Finally, he included among the basic
assumptions of his report one of the more prophetic forecasts of the prewar
years:

War with Japan will be precipitated without notice. One of the most obvious
and vital lessons of history is that Japan will pick her own time for conflict.
The very form of its government lends itself to such action in that its military
and naval forces can, under the pretext of an emergency, initiate and prosecute
military and naval operations independently of civil control .... If and when
hostilities develop between the United States and Japan, there can be little
doubt that the Hawaiian Islands will be the initial scene of action, and that
Japan will apply her available man-power and resources in powerful and determined
attacks against these islands.12

The slight impact of the Drum and Markham recommendations can be credited in
good measure to the rising threat of Hitler's Germany and the increasing prospect
of war in Europe, which from 1938 onward absorbed the major attention of the
Roosevelt administration and of the War Department in particular. Although
the United States Government considered that the Hawaiian Islands lay within
the Western Hemisphere, new plans for hemisphere defense developed after 1938
emphasized the strengthening of the American military position in Atlantic and
Latin American areas. The War Department's stand also reflected the fact that
Oahu, in comparison with other overseas bases or with the continental United
States itself, was already well provided with defenses, and especially with
the means for resisting invasion. It had a full infantry division, a heavy
concentration of coast defense guns, and from 1938 onward the more or less constant
protection of the United States Fleet. But, until 1941, it had no modern Army
combat planes.

One factor that altered the military security of Oahu in the years immediately
preceding the Pearl Harbor attack was the increasing capabilities of

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carrier-based air power. With the nearest Japanese airfield 2,100 miles away,
military authorities correctly calculated that Oahu was beyond the range of
land-based air power; but it could be reached by carriers, of which Japan had
six in operation by August 1939, and two more under construction. In January
1938 Colonel Markham had pointed out how easy it would be for carrier-based
planes to approach Pearl Harbor from the northeast. Screened by the heavy cloud
cap almost continuously present over the main Koolau Range, they could cross
Oahu and deliver a surprise attack on the naval base and its surrounding installations
almost without warning. Since local ground defenses and unwarned pursuit planes
could not hope to cope with such an attack, Colonel Markham assumed that the
Army in order to fulfill its mission would have to conduct long-range aerial
reconnaissance, and he recommended an Army air strength of 350 planes, to
match an estimated 379 planes that Japan might possibly bring to bear in an
initial all-out attack.13

The first War Department plans of 1939 for expanding the Air Corps proposed
to increase the authorized number of Army combat planes in Hawaii from 124 to
256, and to include in the new allotment 140 bombers and 100 pursuit ships. In
its report of June 1939 the Army Air Board explained the large number of bombers
by pointing out the need for Army reconnaissance as well as striking forces to
operate within a 1,000-mile radius of Oahu. Since the Air Board report like all
similar prewar studies recognized that a carrier attack once launched would
inevitably inflict some damage, it pointed out that the only sure means of
preventing successful carrier attacks was to locate the carriers outside a 600-
to 700-mile radius (the range of their attack planes plus one night's sailing)
and bomb them before they could launch their planes. With strength enough to do
this, Army aircraft in Hawaii could also interdict any attempt by the enemy to
establish airfields on any of the other major islands.14

Under the production circumstances of 1939 any plans for strengthening Army
air power in Hawaii were bound to take a long time to carry into effect, but
the initial plans were further limited at the end of 1939 by general assumptions
of the War Plans Division in Washington that Japan would not risk more than
two of its carriers in a surprise attack and that long-range aerial reconnaissance
was properly a Navy and not an Army mission. In the light of these assumptions
the Army planners recalculated Hawaiian needs

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for Army aircraft and allotted the Department 122 pursuit planes and 68 medium
bombers. The bombers were to be used for reconnaissance only if the Navy was
absent or if it asked for reinforcement.15 These two assumptions, that
the Japanese would never employ more than two carriers in a surprise attack
in the eastern Pacific and that Army bombers should not be used for long-range
offshore reconnaissance, remained constants in Washington and Hawaiian defense
thinking and planning for the next two years, and contributed substantially to
Japanese success in December 1941.16

Under the revised 54-group air program of June 1940, Hawaii was allotted some
additional pursuit and light bomber strength for close-in defense purposes and
was scheduled to receive 68 heavy bombers- B-17's -instead of mediums. But the
premises behind the new allotments were still a maximum 2-carrier threat and
performance by the Navy of all long-range reconnaissance.17 During the same month General Marshall suggested sending 5 or 10
B-17's to Oahu immediately, but his G-3 (an Air officer) objected on the ground
that so few would have no restraining influence on the Japanese and would inevitably
be destroyed by hostile pursuit before they could help in fighting off an attack-comments
which throw light on the utility of the 12 heavy bombers (only 6 of which were
in commission) on Oahu on the morning of 7 December 1941.18 What the Hawaiian Air Force actually had at the beginning of 1941
was a heterogeneous collection of 115 combat planes, all of them obsolete or
obsolescent. They were useful almost exclusively for training and not for fighting.19

A second factor affecting the Hawaiian defense picture was the decision to base
the United States Fleet at Pearl Harbor. With Anglo-French naval power seemingly
in control of the Atlantic, the United States continued after August 1939 to
keep the bulk of its naval strength in the eastern Pacific. Until 1940 the principal
bases for the United States Fleet were on the continental west coast, with
Pearl Harbor serving as an advance base and concentration point during
maneuvers. But after annual maneuvers in April 1940 the fleet, under command
of Admiral James O. Richardson, was

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ordered on 7 May to stay at Pearl Harbor, as a warning and deterrent to
Japan. Almost immediately thereafter Hitler's smashing land victory in western
Europe threatened to cripple or destroy Anglo-French naval power in the
Atlantic. To retrieve the situation it appeared by mid-June to Army and Navy
leaders in Washington that the United States would have to transfer the bulk of
its naval strength to Atlantic waters.20

It was this prospect that led General Marshall on 17 June to alert the Panama
and Hawaiian Departments to the danger of a transpacific raid, following the
departure of the United States Fleet. The Chief of Staff and his advisers
reasoned that, as collaborators with Nazi Germany, Japan and the Soviet Union
might launch such a raid in an effort either to keep the United States Fleet in
the Pacific or to block the Panama Canal after its passage into the Caribbean.
They feared a raid against Hawaii only if the fleet had departed, and when
President Roosevelt decided in early July to keep the fleet at Pearl Harbor
their apprehensions about Oahu faded.21

The alert message to Oahu was plain spoken:

Immediately alert complete defensive organization to deal with possible trans-Pacific
raid to greatest extent possible without creating public hysteria or provoking
undue curiosity of newspapers and alien agents. Suggest maneuver basis. Maintain
alert until further notice. Instructions for secret communication direct with
Chief of Staff will be furnished shortly. Acknowledge.22

General Herron reacted with vigor. He ordered a 24-hour manning of all observation
posts and antiaircraft batteries, and for the first time the antiaircraft
gun crews received live ammunition and instructions to fire on any foreign planes
sighted over restricted areas. Airplanes at Hickam and Wheeler Fields were dispersed,
and on 21 June Army planes took over the task of inshore dawn patrols from the
Navy. Although not similarly alerted, Admiral Richardson's forces co-operated
wholeheartedly, instituting both inshore patrols and a limited amount of longer
range aerial reconnaissance the limiting factor being the small number of
Navy planes available for the purpose. On inquiry, the Chief of Naval Operations
confirmed that the Army's alert had been issued after consultation with the
Navy and requested Admiral Richardson to continue his co-operation. On 19 June
the War

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Department authorized a gradual modification of the alert, and a month later
its relaxation at General Herron's discretion, except for continued precautions
against sabotage and local air patrols on a training basis. The Navy maintained
some distant patrolling by Oahu-based sea planes for most of the time until
30 December 1940, when Admiral Richardson discontinued such reconnaissance after
being advised by the Chief of Naval Operations that only naval operating areas
needed reconnoitering.23 In the meantime, the alert measures had fostered
closer co-operation between Army and Navy forces, and in General Herron's opinion
had had a wholly salutary effect on the morale of Army troops. In a personal
letter of 6 September he told General Marshall that "the position of this
place on the Army priority lists is still all right," and assured him that
"as things now are, I feel that you need not have this place on your mind
at all."
24 But on the preceding day he had officially asked for a good
many more antiaircraft troops to man guns already on hand.

The request of Hawaii for more antiaircraft troops reached Washington in the
same month that the United States Government openly shifted its course from
neutrality to nonbelligerency and determination to support Great Britain in
the Atlantic war. To be effective the new course required peace in the Pacific
area, outside of China. But President Roosevelt and his advisers believed that
the United States must also do what it could, short of war, to show Japan that
its open alignment of 27 September with Germany and Italy was not going to stop
American aid to Britain. As one gesture the President directed that Hawaii be
reinforced by a National Guard infantry division, and Secretary Stimson had
some difficulty in persuading the President that under existing circumstances
such a move would really weaken and not strengthen the military security of
Oahu. Partly to satisfy the President's wishes for some sort of reinforcement,
as well as General Herron's plea for more men, General Marshall decided to send
a National Guard antiaircraft regiment from California to Hawaii as soon as
possible. The 251st Anti­aircraft Artillery Regiment, which moved to Oahu
during the winter, was the first National Guard unit to leave the continental
United States for overseas duty in World War II.25

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With strength to man existing ground defense equipment in the offing, General
Herron appears to have been reasonably well satisfied with the Army's posture
of defense on Oahu in late 1940. During November he sent to Washington a paper
entitled Draft Surmises on Insular Operations, his opening surmise being that
fleets could not operate more than 2,000 miles from a major base, although a
small raiding force could range much farther. The implication for Hawaii was
that a small raiding force was all that need be anticipated. The general recognized
the need to detect a carrier raid as far off as possible and acknowledged that
a shore-based aerial patrol was a necessary adjunct to insular defense. But
long-range reconnaissance was the Navy's business, as Admiral Richardson had
informally acknowledged in August.26 And the discontinuance of Navy long-range
patrolling by shore-based planes at the end of the year appears to have
passed unnoticed by the Army.

The absence of an effective shore-based aerial patrol seems to have concerned
General Herron much less than the prospective congestion of the air and of airfields
when the Army and Navy obtained the full quota of planes that had been allotted
to Oahu. The general wondered whether it might not be better to keep most of
the heavy planes allotted to Hawaii on the west coast, on the assumption that
the time had come when the Hawaiian Islands could be largely defended by bombers
based on the mainland. The War Department thought differently, considering
the 68 Army heavy bombers allotted the minimum needed on the spot; and it also
took note of and advised General Herron about the Navy's new plan to station 180 long-range patrol planes in the islands, including
108 that were to
remain permanently to patrol coastal waters and sea lanes. This last increment,
when it arrived, could presumably provide all of the long-range reconnaissance
needed.27 According to his later recollections, what worried General Herron
most at the end of 1940 was the inadequacy of his antiaircraft defenses, not
the present or prospective means of locating and bombing carriers. He told the
Army Pearl Harbor Board in 1944 that he and his air commander had known "that
an air force could come in and do some damage." Continuing, he said:

We hoped to be able to follow them out and destroy the carriers. But I do not
think we had any idea that we could turn back an aerial attack entirely, for
this reason: that

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the only antiaircraft we had was that which was prepared against
high-altitude bombing. We did not have the small-caliber stuff which you need
to do anything about dive bombings. So we felt they could come in; that they
would not come in there unless they had enough planes to overcome what planes we
had.28

From available evidence it appears that as the year 1940 ended the Navy was
more concerned than the Army about the state of the Army's defenses in Hawaii.
After Admiral Richardson discovered on a Washington visit during October that
the President was determined to keep the fleet at Pearl Harbor, he arranged
with General Herron to inspect the Army's defenses and review their adequacy
to protect the fleet and naval installations. His findings became the basis
for a letter from the Secretary of the Navy to the Secretary of War on 24 January
1941, which stressed that Japan might initiate hostilities by a surprise attack
on the fleet and on the base installations at Pearl Harbor, and envisaged an
air attack by bombers and torpedo planes as more probable than threats of sabotage,
submarine attack, the sowing of mines, and bombardment by naval gun fire. The
Navy's estimate did not even mention invasion as a danger, though that was the
preoccupation of a large portion of the Army defenders. The Navy urged "that the
Army assign the highest priority to the increase of pursuit aircraft and
antiaircraft artillery, arid the establishment of an air warning net in Hawaii."
29

The Navy's letter arrived on the heels of a forecast by President Roosevelt
that Japan might even then be preparing to strike at the United States, and
his decision that if that happened the United States must "stand on the
defensive in the Pacific with the fleet based on Hawaii" and continue aid
to Britain.30 The War Plans Division recommended that a few B-17's be sent
to Oahu at once and that Hawaii (as well as Alaska and Panama) be put on a war
basis as soon as possible.31 Even
so, the War Department had drafted a routine response to the Navy's letter,
stating in effect that nothing more could be sent to Hawaii for some time to
come. General Marshall stopped this draft, and arranged to have eighty-one
pursuit planes, fifty of them of the P-40B type, shipped by carriers- to Oahu as
soon as possible.32

The Army answered the Navy's letter on 7 February 1941, the same day that General
Herron relinquished command of the Hawaiian Department to Lt. Gen. Walter C.
Short. A week earlier the Navy had reshuffled its forces, redesignating the
fleet at Pearl Harbor as the Pacific Fleet and giving it a new commander, Admiral
Husband E. Kimmel. The Army command went to General Short because of his reputation
as an effective training man, and he threw himself into the work of his new
post with great energy. General Marshall pointed out to him in a personal letter
of 7 February that "the fullest protection for the Fleet is the
rather than a major consideration" for the Army in Hawaii, and observed
further:

My impression of the Hawaiian problem has been that if no serious harm is done
us during the first six hours of known hostilities, thereafter the existing
defenses would discourage an enemy against the hazard of an attack. The risk
of sabotage and the risk involved in a surprise raid by Air and by submarine
constitute the real perils of the situation. Frankly, I do not see any landing
threat in the Hawaiian Islands so long as we have air superiority.

He also stressed the need for the closest co-operation with the Navy and with
the new Navy commander, Admiral Kimmel.33

For various reasons, concern in Washington over the possible imminence of war
with Japan subsided after February 1941, and worries over recognized deficiencies
in the Army's defense equipment faded once more into the background.

By April, it looked as if the United States was on the brink of open participation
in the Atlantic war, and plans were afoot to reinforce the Atlantic Fleet by
withdrawing a substantial part of the Pacific Fleet from Hawaiian waters. In
the eyes of Washington, Oahu looked more secure than ever, now that it was protected
by some modern Army pursuit craft and was about to be reinforced further by
fifty-five more P-40's and thirty-five B-17's. General Marshall assured Secretary
Stimson that he thought Oahu was impregnable whether any fleet was there or
not, because "with our heavy bombers and our fine pursuit planes, the land
force could put up such a defense that the Japs wouldn't dare attack Hawaii,
particularly such a long distance from home."
34

To assist Mr. Stimson in convincing the President it was safe to shift American
naval power to the Atlantic, General Marshall had the War Plans Division prepare
an estimate, the draft of which read:

The Island of Oahu, due to its fortification, its garrison, and its physical
characteristics, is believed to be the strongest fortress in the world.

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It has been carefully fortified against naval attack and its antiaircraft defense
is relatively complete.

Its total garrison is at present approximately 31,000 men, and is in process
of augmentation by 6,000 men.

Including the movement of aviation now in process, it is defended by 35 of our
longest range bombers, 35 medium range bombers, 105 of our high speed pursuit
ships, 65 fighters, and 13 light bombers.

The Hawaiian Islands are subject to (a) sabotage, (b) carrier raids, (c) an
attack in force.

In point of sequence, sabotage is first to be expected and may, within a very
limited time, cause great damage. On this account, and in order to assure strong
control, it would be highly desirable to set up a military control of the islands
prior to the likelihood of our involvement in the Far East.

Carrier raids by the Japanese involve jeopardizing naval units that will not
be lightly undertaken. To meet these carrier raids our bombardment, protected
by pursuit aviation, the latter operating from advanced fields on the Islands
of Hawaii and Kauai, can cover a radius from Oahu of approximately 400 miles
and beyond suitable points for the establishment of hostile land-based aviation.

An attack in force against Oahu necessitates an air superiority that can only
be had by the establishment of land-based air within striking distance of Oahu.
This can only be accomplished successfully within the Hawaiian group and with
the defense indicated above it is not believed that such establishment
can be accomplished.

Hawaii is capable of reinforcement by heavy bombers from the mainland by air.35

A note (by the President's military aide) on a revised version handed to Mr.
Roosevelt summed up the War Department's optimistic view: "Modern planes
have completely changed situation as to defensibility."
36 The principal
effect of these arguments seems to have been to plant a new legacy of confidence
among Washington leaders in the immunity of Hawaii from serious attack, since
the President decided then and thereafter that the bulk of the Pacific Fleet
must remain in the western Pacific as a deterrent to Japanese aggression.37

When General Short surveyed his new command in February 1941, he recognized
a good many more flaws in its armor than the War Department in Washington did
two months later. Although he appears never to have been greatly concerned during
1941 about the number of Army aircraft on hand and ready for action, he did
take an intense interest in other matters related to air defense. Prompted by
General Marshall's personal letter of 7 February and an official War Department
communication of the same date, General Short turned his attention at once to
improving co-operation

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between Army and Navy forces and in particular to clarifying the respective
responsibilities of their air forces in defensive operations.38

At the beginning of 1941 Army and Navy forces in Hawaii, as everywhere
else in the field, operated more or less independently of each other, with co-ordination
as circumstances required under the principle of mutual co-operation. On paper
responsibility for local naval defense measures except aboard ship rested with
the commandant of the Fourteenth Naval District, Rear Admiral Claude C. Bloch,
and it was with Admiral Bloch's organization that the Army command proceeded
to negotiate on a number of matters pertaining to air defense. Actually the
Fourteenth Naval District had no defense forces of its own during 1941, and
the contribution that the Navy could make to local defense depended upon what
could be spared from the fleet and its Marine Corps attachments. It therefore
depended also on the maintenance of a close personal relationship and understandings
between General Short and Admiral Kimmel, the fleet commander.

Their predecessors, General Herron and Admiral Richardson, had succeeded in
overcoming some of the characteristic resistance to effective Army-Navy co-operation
in the field. An aftermath of the spring maneuvers and subsequent alert of 1940
had been an informal joint agreement on air operations under which the Navy
assumed exclusive responsibility for distant reconnaissance, both services retained
the right to conduct close-in reconnaissance for their own protection, and each
might engage independently in air attacks against a hostile fleet.39 The new formal agreement signed by General Short and Admiral Bloch
on 28 March 1941 left responsibility for distant reconnaissance with the Navy,
but if Army planes helped out they were to operate under Navy command; if Navy
planes helped in the defense of Oahu's land area, they were to operate under
Army command; and any Army bombardment planes engaging in offensive operations
at sea were to be under Navy command.40 In joint exercises during 1941 the new agreement worked well enough;
but the prejudice in both services against unity of command offered fair assurance
that except in such exercises the agreement would not be invoked unless a compelling
and clearly recognized emergency was at hand.

In another joint paper signed three days later, the Army and Navy air commanders
in Hawaii acknowledged how difficult it might be to foresee

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such an emergency. Their estimate of the outlook emphasized the possibility
of a sudden Japanese attack on Oahu prior to a formal declaration of war, and
they noted the likelihood under existing circumstances that a dawn air attack
launched from carriers might hit at the fleet and naval installations at Pearl
Harbor with such complete surprise that defending pursuit could do little to
soften the blow. They recognized that distant air reconnaissance was the best
defense against surprise. Pointing out that it would be impossible with the
equipment at hand to maintain such reconnaissance except for a short period,
they emphasized the necessity of obtaining intelligence that a raid on Oahu was
imminent before undertaking a systematic long range reconnaissance of its sea
approaches.41

In addition to pushing toward agreement on other matters of mutual concern to
the two services, General Short made a point of cultivating the personal friendship
of Admirals Kimmel and Bloch. In forwarding the items described above to General
Marshall, he stated that he had found both admirals most co-operative and that
they all felt that steps had already been taken to make it possible for Army
and Navy forces to act together and with the unity of command that the situation
might require. Somewhat later Admiral Kimmel reported to Washington in the same
vein, but noted the serious need for a great many more Army heavy bombardment
planes.42

Instead of receiving 35 B-17's as planned in April, only 21 made an historic mass flight from California to Oahu in mid-May. The critical outlook of
affairs in the Atlantic area induced General Marshall to withhold the other
14.43 Early in July the War Department was wondering whether more than one
35-plane group of heavies was really needed in Hawaii before the outbreak of
a war, and even the Hawaiian Air Force commander optimistically estimated
in August that one such group would be strong enough to finish off six enemy
carriers. The real need, he felt, was for long-range reconnaissance; and, ignoring
the Navy's responsibility for this function and plans for undertaking it eventually,
he asked for a total of 180 heavy Army bombers so that the Army could do it.
His request, warmly endorsed by General Short, reached Washington in the midst
of new War Department planning that allotted from 136 to 204 heavy Army bombers
to the Hawaiian

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Department by mid-1942, and this planning had to suffice as an answer for the
time being. These plans also coincided with the new Washington decision to reinforce
the Philippines, and the net result was that Oahu lost 9 of its 21 heavies to
the Philippines in early September and kept the remaining 12 only because they
could be employed most usefully at Hickam as sources of spare parts and in
training new combat and ferry crews.44

Superficially, Oahu's needs for pursuit craft appeared much better met. During
most of the time between May and December 1941 it had about 150 Army pursuit
and fighter planes, two-thirds of them modern P-40's. But a chronic shortage
of spare parts kept many of these planes out of commission, and the ones available
had to be used intensively for training. The greatest qualification was that
pursuit planes, however modern, were all but worthless as defense equipment in
the absence of an effective warning system, and Oahu had none before the attack
on Pearl Harbor.45

In early December 1941 the Army did have an aircraft warning system nearing
completion in Hawaii, but it was not yet in operation. This system depended
for its information on the long-range radar machines developed by the Signal
Corps in the late 1930's, the SCR-270 (mobile) and SCR-271 (fixed). The Signal
Corps in Washington drafted the first plan for installing some of this
equipment in Hawaii in November 1939, but before 1941 not much actually was
done to prepare for its installation.46 As of February 1941 the War Department
expected to deliver radars to Hawaii in June and hoped they could be operated
as soon as they were delivered. The first mobile sets actually reached Hawaii
in July, delivery having been delayed by about a month because of a temporary
diversion of equipment to an emergency force being prepared for occupation of
the Azores. In September five mobile sets began operating at temporary locations
around Oahu, and a sixth, the Opana station at the northern tip of Oahu,
joined the circuit on 27 November. Three fixed sets also arrived during
November, but their mountain-top sites were not ready to receive them.47

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The radars in operation on Oahu in late 1941 had a dependable
range of from 75 to 125 miles seaward. An exercise in early November
demonstrated their ability to detect a group of carrier planes before daylight
80 miles away, far enough out to alert Army pursuit planes in time for the
latter to intercept incoming "enemy" bombers about 30 miles from Pearl Harbor.
But this test in no way indicated the readiness of radar to do its job a month
later. The sets were being operated solely for training; a shortage of spare
parts and of a dependable power supply made it impracticable to operate them for
more than three or four hours a day; the organization for using their
information was a partly manned makeshift operating for training only; and
defending pursuit, even if they could have been informed, would have had to keep
warmed up and ready to take off in order to intercept enemy planes before they
reached their targets.

The radars were not supposed to function except for training
purposes until the Signal Corps turned them over to an air defense or
interceptor command, to be operated by the Army pursuit commander through an
information center which would receive data from the radar stations, warn the
defending pursuit, control the movement of friendly planes, and control the
firing of all antiaircraft guns. In March 1941 General Short had agreed that
Hawaii needed such a command, and he arranged for his pursuit commander and his
Signal Corps officer to visit the continental United States in the late fall of
1941 to witness operations and exercises of interceptor commands, preparatory to
installing the system in Hawaii. They did not get back to Oahu until 4 December,
much too late to get a local interceptor organization and information center
into operation before the Japanese attacked.

The Army generally had more confidence in late 1941 in a much
older weapon, the antiaircraft gun, as a means of air defense. Antiaircraft
artillery had played an important part in the defense planning and preparation
of the Hawaiian Department since 1921, when it organized the first antiaircraft
artillery regiment in the United States Army. Twenty years later the latest
revision of the Hawaiian defense project, approved by the War Department in
September 1941, prescribed an impressive allotment of antiaircraft artillery
weapons: 84 mobile and 26 fixed 3-inch guns for high altitude firing, and
provision for replacing some of them as soon as possible with more modern
weapons; 144 of the newer 37-mm. automatic weapons; and 516 caliber .50
antiaircraft machine guns for action against low-flying aircraft. By then also
the department had four antiaircraft regiments, and it was scheduled to receive
a fifth before the end of the year. Actually three

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of the four regiments present were at little more than half
strength, and the equipment on hand was considerably less than that allotted,
amounting to 60 mobile and 26 fixed 3-inch guns, only 109 antiaircraft machine
guns, and only 20 of the 37-mm. automatic weapons.48

With the strength available, Army antiaircraft on Oahu had
the ability when deployed to give some protection against high-flying horizontal
bombing planes along the south coast (from Diamond Head to west of Pearl Harbor)
and around Schofield Barracks and Wheeler Field. The 37-mm. guns had been in
Hawaii for almost ten months before ammunition for them arrived on 5 December
1941, and there had been very little for the antiaircraft machine guns, so that
firing practice for even the small number of guns available for defense against
dive or torpedo bombers or other low-flying planes had been more or less out of
the question. About half the mobile 3-inch guns were assigned action stations on
private property, and in practice sessions during the months before the Japanese
attack the gun crews kept to nearby roads and carefully refrained from
trespassing.49
Except during practice sessions the guns and the regiments that manned them were
concentrated in three areas some distance from their battle stations, and at all
times after May 1941 ammunition for the guns remained in the Ordnance depot.
Only the fixed 3-inch guns, with ammunition boxed but close at hand, were ready
for near immediate action. The rest depended on getting several hours' advance
warning of an impending attack.

When General Short assumed command in February 1941 he immediately
recognized the need for giving greater protection to Army aircraft on the ground
by constructing dispersal runways and bunkers at existing airfields, and by
building new airfields on Oahu and on other islands to relieve the congestion
and close concentration of planes at Hickam and Wheeler Fields. By May the War
Department had given formal approval to the construction to 253 bunkers, but
it failed to provide any funds or to approve plans for them before the Japanese
attacked in December. During the summer General Short by using troop labor managed
to construct 85 bunkers at Wheeler Field; but under the alert of 27 November
planes were ordered to be bunched not dispersed, and the bunkers therefore were
not put to use.50

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On Oahu during 1941 the Army completed and opened the new Bellows Field on
the coast east of Honolulu, and it was being used in the fall by pursuit and
light bomber planes. General Short wanted to build another pursuit field on
the plateau about four miles northeast of Schofield Barracks, but the War
Department insisted that it be located on the northern tip of Oahu, at Kahuku
Point, instead. Because of this argument, and the fact that the Kahuku site
was being used by the Navy as a bombing range, a new major pursuit field on
Oahu remained no more than an idea before December.51A small training field,
near Haleiwa in the same area, was unknown to the Japanese and almost
untouched by them in the Pearl Harbor attack. The Army also made arrangements
with the Navy for the practice use of each other's airfields on Oahu and on
other islands of the Hawaiian group, and for the extension of runways on Navy
fields to accommodate Army heavy bombers.52

The development of military airfields in the outer islands harked back to plans
of the 1920's and 1930's for the establishment of air bases on Hawaii and Kauai.
Fields on these and other islands were begun in June 1940 by the Works Progress
Administration in accordance with priorities established by the Army. A year
later the War Department approved new construction that would allow the operation
of heavy bombers from two fields on Kauai and three on Hawaii and would permit
pursuit planes to operate from fields on Molokai and Lanai. Completion of these
projects would make possible the distant dispersion of bombers from Hickam,
and pursuit ships could be flown to the nearest islands. But no Army aircraft
had occupied the new fields before 7 December.53

The beginnings of military airfield construction on other major islands, together
with General Short's concern about the possibilities of sabotage or other hostile
action by residents of Japanese descent, prompted the first garrisoning
of the Hawaiian group as a whole by active Army forces. In May 1941 General
Short detached the 299th Infantry Regiment from the Hawaiian Division and sent
one battalion to Hawaii, another to Kauai, and divided a third between Maui
and Molokai.54 These detachments and other Army forces sent to the outer
islands were put under the local command of

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military districts (of Hawaii, Maui, and Kauai) which in turn reported
directly to the commander of the Hawaiian Department. Trained combat troops on
the outer islands numbered about 1,300 at the beginning of December 1941.55

About the same time that General Short decided to garrison the outer islands
he asked the War Department to approve the reorganization of the Hawaiian
Division by distributing its four infantry regiments between two new triangular
divisions. The actual reorganization, into the 24th and 25th Infantry Divisions,
did not become effective until 1 October 1941. The new divisions had an
authorized strength of about 11,000 officers and men each, but their actual
strength was considerably less at the outset, and the 24th Division had no
control over the battalions of the 299th infantry scattered among the outer
islands.56

In the year preceding the Pearl Harbor attack, the Army's officer and enlisted
strength in the Hawaiian Department grew from 28,798 to 43,177, and Hawaii remained
the largest of the overseas garrisons.57 Nearly half the increase represented
increments, including a good many men of Japanese descent, drawn from the local
population through the induction of the National Guard and the operation
of the selective service system.58 Since most of the new men received from
the mainland also needed more training, the Hawaiian Department of necessity
became a training establishment on a large scale during 1941, resembling in
many respects the ground and air training commands then so active in the continental
United States.

Until 28 May 1941 the RAINBOW plans contemplated an Army wartime garrison of
79,000 for Hawaii, substantially less than had been scheduled for it in war
plans of the mid-1930's.59 On that date the War Department ordered a further
reduction of 21,000 and lessened the decrease only slightly to accommodate
General Short's plan for additional units to guard the Navy's new air station
at Kaneohe Bay on the northeast coast of Oahu.60 By 22 September 1941, when
Secretary Stimson and General Marshall went

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over the strengths of all overseas garrisons with President Roosevelt, Hawaii
had its full authorized peacetime strength of about 42,000. They agreed that
any further reinforcement of the Hawaiian garrison could be deferred as long
as the fleet remained in the Pacific, since the presence of the fleet reduced
the threat of major attack.61 The revised RAINBOW 5 plan of November 1941
called for 17,300 more troops to be sent as war reinforcements as soon as possible,
and an ultimate war garrison of about 68,000.62 Behind
all these figures appears a confidence in Washington during 1941 that Hawaii by
comparison with other overseas outposts was well manned, and that in the event
of war Hawaii would not be on the front line of conflict as forecast by the
larger war garrisons planned for it by the Army during the 1930's.

The same confidence can be deduced from war plans drafted and approved
by the War Department during late 1941. Back in August 1937 Army and Navy planners
had put the Hawaiian Coastal Frontier into Category of Defense D, which
indicated an area that might be subject to major attack and within which all
elements for defense should be approximately ready for action or in action,
including an active antiaircraft gun defense of important areas and long-range
aerial reconnaissance as required. Actually this provision meant very little
either before or after the Pearl Harbor attack, since even after the attack
the Category D description remained unchanged until October 1943, and at
no time did it reflect with any accuracy the current status of defense operations.
The War Department's RAINBOW 5 Operations Plan, approved 19 August 1941, confirmed
Category of Defense D, and stated the Army's mission to be: "Hold
Oahu against attacks by land, sea, and air forces, and against hostile sympathizers.
Support naval forces in the protection of the sea communications of the Associated
Powers and in the destruction of Axis sea communications by offensive action
against enemy forces or commerce located within tactical operating radius of
occupied air bases."
63 The provision for the support of naval forces was
inapplicable until the Navy put its operating plans based on RAINBOW 5 into
effect, an action which it did not take except in areas many thousands of miles
from Hawaii until after the Japanese attacked. A month later, on 17 September,
the War Department approved the latest revision of the

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Hawaiian Defense Project, which listed the forms of possible enemy attack in
the following order of probability:

(a) Submarine-torpedo and mine.
(b) Sabotage.
(c) Disguised merchant ship attack by blocking channels, by mines, or by air
or surface craft.
(d) Air raids, carrier based.
(e) Surface ship raids.
(f) Major combined attack in the absence of the U.S. [sic] Fleet.64

Thus, sabotage was again confirmed as the principal and immediate concern
of Army defense forces. Finally, in the revision of RAINBOW 5 completed in
November, the Washington planners limited the sea area required for the defense
of Oahu to a 500-mile radius from land, a limitation which if it had been
applied would have confined long-range reconnaissance to bounds that all
previous studies had considered ineffective for detecting the approach of
carrier forces before they could launch their planes.65

Thus, though extensively reinforced, the Army defenses of Oahu were not ready
by 7 December 1941 to detect the approach of a carrier attack or to cope with
an air attack as powerful as that launched by the Japanese.